[Histopathology of metastatic bone tumors]

Overall bone metastasis (BM) was found upon autopsy in 271 (26.0%) of 1041 patients who died due to malignant epithelial neoplasm at our hospital over the last 20 years. The incidences of BM from primary organs were as follows; 71.4% for breast cancer, 70.0% for prostate, 49.6% for lung and 22.5% for stomach. The distribution of skeletal metastases was the lumber spine in 63.8% of cases, sternum in 38.0% and ribs in 26.2% as revealed by routine autopsy examination. The most common pathway of BM was the transpulmonary route, followed by the vertebral venous system which is known to be involved in metastasis to the spine. The frequency of BM via the vertebral venous system without pulmonary metastasis was 30% for carcinoma of the prostate, 10.4% for the uterus, 7.4% for the breast and 3.5% for the stomach in our examination series. Types of focal reaction to BM were classified as osteoplastic (OP), osteolytic (OL), intertrabecular and mixed types. The mixed type showed transitional and mixed features between OP and OL types. Therefore they were considered to be closely related. Relationships between primary organs and histologic appearances revealed a degree of specificity for BM. Squamous cell carcinoma in various organs and small cell carcinoma of the lung appeared to produce an OL but not OP reaction. OP was especially characteristic of prostatic cancer, poorly differentiated adenocarcinoma of the stomach and breast, in young patients. There appeared to be a relation between clinical course and the form of treatment for metastatic bone reaction.